One visit to a Palladian villa and approximately 700 boxwoods ago, Richard Shapiro's garden was just another Southern California backyard with a manicured lawn, some palm trees, and a 1950s swimming pool. But the Los Angeles–based antiques dealer and designer of the Studiolo home-furnishings line had far more ambitious dreams. "My objective was to create an eccentric garden in a setting of fantastical Mediterranean antiquity," he says.

After living for more than two decades in an atmospheric 1920s villa (which he has restored to its original Spanish-and-Moroccan-via-Hollywood glory), Shapiro decided that improving the land around it was the next step. For inspiration he drew on the experiences of his years spent touring Europe, first as an avid art collector and then as a buyer for his own gallery. And what was the environmental theme the dealer eventually settled on? "It's about self-deception," he says with a grin.

To keep 21st-century Los Angeles at a distance, Shapiro wrapped the grounds with 20-foot-high ficus hedges and stands of giant Japanese timber bamboo. "I wanted complete seclusion and mystery," he explains. At the far end of the formerly banal pool—now camouflaged with algae-green paint and distressed-stone coping—a Roman-style temple rises from the chlorinated mists. A full-scale recreation of a neoclassical portico, complete with 21-foot-high columns, it has been built precisely as architect Andrea Palladio drew it in the 16th century. "When I'm interested in something, I study it microscopically," says Shapiro, who visited the original structure at Villa Chiericati in the Veneto region of Italy and then found its plans in a book. Shapiro replicated the stone Ionic columns in carved redwood with resin capitals and fiberglass bases. Then, with the help of a set designer, he aged them with a mixture of plaster, lime, and spray-painted moss. Real antiquities enhance the faraway atmosphere: A fragment of a fourth-century Roman column, 17th-century Florentine marble lions, and a 10-foot-tall antique Spanish oil pot are tucked amid the twisting gravel paths and along the Provençal-style walk edged with lavender, rosemary, and cypresses.

Palladio's portico was designed as the frontispiece of a country house, but its L.A. twin functions as a 275-square-foot living area centered on a 19th-century mantel Shapiro discovered in Antwerp. To age that antique, which had been overrestored, the dealer darkened it with artful soot stains. "You can't imagine how many things I burned to get the staining right," he says. "In the end, old wicker chairs worked best." Everyone calls Shapiro's temple a folly—by definition a decorative structure with no purpose—but the dealer describes it as the room he uses most often. In the mornings, he lights a fire and reads newspapers with a cup of coffee; in the evenings, guests gather for drinks, nestling into comfortable banquettes and chairs covered in a casual combination of red-and-white-striped cottons. Joining them are designs for Shapiro's Studiolo line, such as the mirror hanging over the fireplace. He also constructed an atelier for making his own sculptures and paintings; it has evolved into a contemporary area for entertaining.

As Shapiro admits of his compound, "There's scarcely a square foot that I haven't modified." But the star attraction was not achieved until a few years ago, after a visit to Château de Marqueyssac in the Dordogne region of France. The castle's snakelike topiary hedges spurred Shapiro to create his own versions. "The undulating forms reminded me of Japanese cloud painting," says the dealer. "I'm an obsessive person as a collector, and I realized that whoever designed that garden was just as obsessive."

Back home, Shapiro, duly inspired and ready for action, ripped up the expansive lawn and imported hundreds of mature boxwoods from a grower in Oregon. Next he laid out a swirling planting scheme with chalk and spray paint, added narrow gravel paths for a labyrinthine effect, and began enthusiastically planting and clipping. "It was an exhilarating and freewheeling exercise," Shapiro reports. "I could instantly see the results of my work." Within a year new growth filled in the holes he had sheared, and the garden looked as though "it had been there forever."

Though Shapiro has help maintaining the grounds, the designer-dealer is the only person allowed to touch up the intricate hedges, a job that takes surprisingly little time—almost no effort in the winter and some clipping every two weeks in the summer. "I view the garden as a vast abstract canvas," Shapiro says. "It is great exercise, great therapy, and a great pleasure." Still, he observes after a pause and a smile, "People think I'm mad, but in a nice way."